[MJK]

I am not convinced of a H-frame together with Alphas. The additional airload will lead to a smeared bass reproduction.

How does additional air load lead to a smeared bass? What is smeared bass, what does it sound like?

Do you believe this is a property of all H frames or just the Alpha 15A driver?

Do you believe this is also true of U frames?

[Poultrygeist]

same64,

I've found the simplest and strongest method for mounting the upper driver is an inverted T using a Kreg Jig and pocket hole screws plus Titebond wood glue. Mine require no bracing and is so strong I could literally stand on it. Using a base the same size as the H-frames makes for added stability and allows the inverted T to rest on the H-frames without the need for fasteners. I sandwich dampening material between the two.

I plan to use this with the Beta 12LTA and Peavey tweeters.

[puppet]

I've been experimenting with OB for a little while and think that the "smeared bass" phenomenon comes from asking too much from the driver ... as in trying to go too low in frequency. Any driver will lose control at some point ... the cone excursion seems to start to conflict with sound reproduction, at least from what I've sensed.   ... and whether it's in a H or U frame doesn't seem to matter too much (as far as driver misuse is concerned).

[Badwater]

Something like this?

http://gallery.me.com/marilynladieu#100295/IMG_2021&bgcolor=black

Alpha 15A
EV SP12B
Fostex T90A

Bill

[Poultrygeist]

Bill, I like the looks of it. Gotta sound nice.

[Badwater]

They sound very nice, very smooth and detailed.  The EV is just a wonderful driver.  i bought the EV's new in 1975 and they always delight.  I like that it can reach down low to meet the Alpha with out straining.   

Right now they are out of commission.  The crappy plate amp that I was using drive one of the H frames failed.  I plan to work up an MJK crossover and run them passive. The top end will need to be attenuated to match the EV and Fostex.  Anybody have any thoughts about using and autotransformer L-PAD?

Thanks,

Bill

[Gothover]

I've been partial to these designs from an aesthetic point of view. I will be posing pictures of my latest build soon that both my wife and I like the looks of...

Great looking speakers.

Dave

[same64]

Hi there.
Finally i finished OB .
What you think guys?.

[Poultrygeist]

Nice job. They look great. I'm glad others are trying this combination as I'm sure enjoying mine. To hide the difficult to stain plywood ends I've resorted to using cheap screen door molding.

[Poultrygeist]

I cut out the dust cap on my Betas and replaced them with some homemade phase plugs which are nothing more than wooden Easter eggs with flat bottoms. I found them at AC Moore Craft Shop for $1.00 and they fit perfectly. Counter sunk two wood screws in the base so they attach magnetically. The highs are now smoother.
 

[mightym]

Poultrygeist,

What tweeter is that in your pic w/ 12LTA and phase plug?

What are  you using for XO?

John

[Poultrygeist]

Those are P.E. Peavey's with a 1 uf cap which I'm driving separately with their own t-amp.

[mightym]

Thank you.

MCM has a similar looking tweeter.  PE show's it as a buyout NLA.

John

[same64]

I cut out the dust cap on my Betas and replaced them with some homemade phase plugs which are nothing more than wooden Easter eggs with flat bottoms. I found them at AC Moore Craft Shop for $1.00 and they fit perfectly. Counter sunk two wood screws in the base so they attach magnetically. The highs are now smoother.
 

Hi
will try phase plugs later on.
I want to finish multi channel Tk2050 amp first and setup the way i want.Then i can experiment with different minidsp settings.
Would the more expensive cap for tweeter make any defference?.

best regards

[Poultrygeist]

The cap I used is a Dayton PMPC. I doubt anything more expensive would make much of a difference but of course I'm no more than a novice at all this.

A friend from out of town came by over the weekend for a first listen. He is a professional violinist with an electronics background and builds tube gear. I had previously sold him my Zu's which he still enjoys. But after hearing the Beta/Alpha H-frames he now wants me to build him a pair. I was flattered.